1. Field of the Invention
The invention relates generally to a semiconductor structure and method of manufacturing and more particularly to a pFinFET with a buried channel and a method of manufacturing.
2. Background Description
Fin field-effect transistors (FinFETs) are MOSFET double-gate transistors built on an SOI/bulk semiconductor substrate. In implementation, the gate is wrapped around the channel of the FET, forming a double gate structure. The FinFET device has significantly better control of short channel effect and higher or equivalent current density than conventional CMOS technologies, and may be used in almost all types of integrated circuit designs (i.e., microprocessors, memory, etc.).
In particular, the use of the double gate suppresses Short Channel Effects (SCE), provides for lower leakage, provides for more ideal switching behavior, and reduces power consumption. In addition, the use of the double gate increases gate area, which allows the FinFET to have better current control, without increasing the gate length of the device. As such, the FinFET is able to have the current control of a larger transistor without requiring the device space of the larger transistor.
In fabrication processes, high quality relaxed SiGe layers on Si has resulted in the demonstration of FETs with enhanced carrier channels. Also, using Ge in the channel can enhance hole channel mobility. Although the physics of carrier scattering are not known inside short-channel FETs, it is known that the enhanced mobility translates into increased device performance, even at very short gate lengths.
To increase mobility, a buried channel can be used for single gate MOSFET. The buried channel can keep carrier away from scattering of gate dielectric interface and then enhance carrier mobility or MOSFET performance. However, MOSFET with a buried channel has worse SCE than conventional MOSFET due to losing some control of the gate to channel electric potential. It is preferable to use double gate structure for buried channel MOSFET in order to obtain high performance as well as good SCE since double gate MOSFET gives good SCE.